1 files changed, 77 insertions, 0 deletions
diff --git a/devtools/shared/throttle.js b/devtools/shared/throttle.js
new file mode 100644
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+++ b/devtools/shared/throttle.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * From underscore's `_.throttle`
+ * http://underscorejs.org
+ * (c) 2009-2014 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
+ * Underscore may be freely distributed under the MIT license.
+ *
+ * Returns a function, that, when invoked, will only be triggered at most once during a
+ * given window of time. The throttled function will run as much as it can, without ever
+ * going more than once per wait duration.
+ *
+ * @param  {Function} func
+ *         The function to throttle
+ * @param  {number} wait
+ *         The wait period
+ * @param  {Object} scope
+ *         The scope to use for func
+ * @return {Function} The throttled function
+ */
+function throttle(func, wait, scope) {
+  let args, result;
+  let timeout = null;
+  let previous = 0;
+
+  const later = function() {
+    previous = Date.now();
+    timeout = null;
+    result = func.apply(scope, args);
+    args = null;
+  };
+
+  const throttledFunction = function() {
+    const now = Date.now();
+    const remaining = wait - (now - previous);
+    args = arguments;
+    if (remaining <= 0) {
+      clearTimeout(timeout);
+      timeout = null;
+      previous = now;
+      result = func.apply(scope, args);
+      args = null;
+    } else if (!timeout) {
+      timeout = setTimeout(later, remaining);
+    }
+    return result;
+  };
+
+  function cancel() {
+    if (timeout) {
+      clearTimeout(timeout);
+      timeout = null;
+    }
+    previous = 0;
+    args = undefined;
+    result = undefined;
+  }
+
+  function flush() {
+    if (!timeout) {
+      return result;
+    }
+    previous = 0;
+    return throttledFunction();
+  }
+
+  throttledFunction.cancel = cancel;
+  throttledFunction.flush = flush;
+
+  return throttledFunction;
+}
+
+exports.throttle = throttle;